Biomedical subjects

Ichiro Koyama

Publications and source records attributed to Ichiro Koyama.

7 recordsLinked to original sources

PubMed2006

Monitoring antidonor alloantibodies as a predictive assay for renal allograft tolerance/long-term observations in nonhuman primates.

BACKGROUND: In an effort to define reliable assays that might predict postimmunosuppressant-withdrawal development of chronic rejection (CR), despite conditioning for tolerance induction, we evaluated various immunological responses in nonhuman primate renal allograft recipients. METHODS: Fourteen Cynomolgus monkeys received low dose total body irradiation, thymic irradiation, antithymocyte globulin, and peritransplant CD154 blockade, followed by a one-month course of cyclosporine. Recipients underwent major histocompatibility complex mismatched kidney transplantation with donor bone marrow infusion (Group A, n=8), without donor cell infusion (Group B, n=2), or with donor splenocyte infusion (Group C, n=4). RESULTS: All Group A recipients developed mixed chimerism and four of them survived long-term without rejection. The remaining four rejected their kidney allografts either chronically or acutely. All recipients in Groups B and C failed to develop chimerism and rejected their allografts. Among various in vitro assays, detection of anti-donor alloantibody (ADA) by flow cytometry (FCM) was the most relevant to long-term outcome. All five recipients that developed both anti-T cell and B cell IgG ADA in Groups A, B and C, developed histological evidence of CR within 200 days of the appearance of ADA. One of two recipients that developed only anti-B cell IgG ADA eventually developed CR over two years following discontinuation of immunosuppression and 1.5 years after ADA development. Another recipient with very low anti-B cell ADA has never developed CR. CONCLUSION: ADA monitoring with FCM assay appears to be useful in predicting the failure of tolerance prior to the development of functional or histologic abnormalities of the renal allograft.

Animals↗

PubMed2006

Early steroid withdrawal protocol with basiliximab, cyclosporine and mycophenolate mofetil in renal-transplant recipients.

OBJECTIVE: Adverse effects of steroids have led to efforts to minimize their use in recipients of organ transplants. This study evaluated an early steroid withdrawal protocol including basiliximab, cyclosporine (CsA) and mycophenolate mofetil (MMF) in renal-transplant recipients. METHODS: Between January 2001 and April 2005, our early steroid withdrawal protocol was used in 130 patients who underwent renal transplantation. Immunosuppression consisted of CsA (6-8 mg/kg), MMF (2 g/kg) and methylprednisolone (MP); basiliximab was given as induction therapy (steroid withdrawal group). MP was administered in a dose of 500 mg or 250 mg at renal transplantation; thereafter, the dose was rapidly tapered and MP was withdrawn on day 14 post-transplant. RESULTS: The incidence of acute rejection in the steroid withdrawal group was similar to that in the conventional steroid treatment group (without basiliximab) (18% vs. 21%). The severity of rejection episodes was similar in the two groups. Patient and graft survivals were 100% and 97% in the steroid withdrawal group. In 80 of the 130 patients (62%) in the steroid withdrawal group, MP was successfully withdrawn, with good allograft function during follow-up. In the other 50 patients (38%), MP was reinitiated because of acute rejection or other reasons. The success rate of steroid withdrawal 12 months after transplantation in recipients of ABO-compatible grafts was significantly higher than that in recipients of ABO-incompatible grafts (66% vs. 44%). The dose of MMF during the 12 months after renal transplantation was significantly lower in steroid reinitiated group than in the successful withdrawn group (p<0.05). Patients in the successful withdrawn group showed metabolic benefits such as lower cholesterol levels as compared with the steroid reinitiated group. CONCLUSION: Although further follow-up is necessary to confirm our results, our protocol successfully permitted the early withdrawal of steroids in 62% of renal-transplant recipients, with no resumption of steroid treatment during 3 years of follow-up.

ABO Blood-Group System↗

PubMed2004

Thrombophilia associated with anti-CD154 monoclonal antibody treatment and its prophylaxis in nonhuman primates.

BACKGROUND: The authors previously reported thromboembolic complications associated with anti-CD154 monoclonal antibody (mAb) treatment in nonhuman primates. The underlying mechanisms of this complication and its management have not been established. METHODS: Eighty cynomolgus monkey renal allograft recipients treated with anti-CD154 mAb were studied for the incidence of thrombosis and its prophylaxis. RESULTS: Without anticoagulation prophylaxis, thromboembolic complications were seen in 5 of 11 recipients. With addition of perioperative heparin, the incidence was decreased to 2 of 10. No further improvement was observed by adding intraoperative prostaglandin (PG) E1. However, addition of ketorolac tromethamine to PGE1 and heparin decreased the incidence of thrombosis (one of eight). Most recently, the authors have found that ketorolac administration alone resulted in no thrombosis in 25 consecutive recipients. CONCLUSIONS: Ketorolac is remarkably effective in preventing thromboembolism associated with anti-CD154 mAb treatment, suggesting the mechanism underlying this complication may be related to platelet activation leading to enhanced aggregation.

Alprostadil↗

PubMed2004

CD154 blockade for induction of mixed chimerism and prolonged renal allograft survival in nonhuman primates.

Costimulatory blockade with anti-CD154 monoclonal antibody (aCD154) prolongs allograft survival in nonhuman primates, but has not reliably induced tolerance when used alone. In the current studies, we evaluated the effect of adding CD154 blockade to a chimerism inducing nonmyeloablative regimen in primates. We observed a significant improvement of donor bone marrow (DBM) engraftment, which has been associated with a lower incidence of acute rejection and long-term survival of renal allografts without the need for previously required splenectomy. Among the long-term survivors, four never showed evidence of rejection, with the longest survival exceeding 1700 days following discontinuation of immunosuppression. Nevertheless, late chronic rejection was observed in three of eight recipients, indicating the necessity of further modifications of the regimen. Control recipients receiving no DBM or donor splenocytes in place of DBM rejected their allografts. Thus, DBM engraftment with, at least, transient mixed chimerism appears essential for induction of allograft tolerance using this conditioning regimen. Modification of the original mixed chimerism approach, by the addition of costimulatory blockade, has been shown to enhance mixed chimerism and induce renal allograft tolerance with less morbidity in nonhuman primates.

Animals↗

PubMed2002

Living related liver transplantation for polycystic liver disease.

Polycystic liver disease (PCLD) is a rare inherited disorder, often associated with polycystic disease of the kidney. Although liver failure is unusual, some patients suffer from hepatic enlargement associated with severe complications such as abdominal distention, cachexia and dyspnea. Until recently, many surgical attempts had been made to reduce hepatic size, however, results have been unsatisfactory [3, 9, 10]. Today, liver transplantation is recommended as a therapeutic option, and excellent outcome has been demonstrated [1, 2, 4, 5, 6, 8, 11]. In this paper, we present the first case study of total hepatectomy and partial liver transplantation for PCLD, from a living, related donor. The patient is a 38-year-old man with PCLD who underwent living related liver transplantation (LRLT). He is alive and well 21 months after the operation, with complete resolution of the symptoms. He has returned to his previous job, with a marked improvement in his quality of life. Our experience demonstrates that LRLT can be an option for treatment of PCLD.

Adult↗

PubMed2002

Large-area phase-contrast X-ray imaging using a two-crystal X-ray interferometer.

Large-area (25 x 20 mm) phase-contrast X-ray imaging was attained by using a skew-symmetric two-crystal X-ray interferometer. The sub-nrad angular control required to operate the X-ray interferometer was achieved with a sleeve bearing and a feedback-positioning system. As a demonstration, measurements of a phase map of a rat's liver and a phase-contrast tomographic three-dimensional image of a piece of a rabbit's liver were performed at the Photon Factory using 0.07 nm synchrotron radiation X-rays.

Animals↗

PubMed2002

[Evaluation of efficiency of a semiconductor gamma camera].

We evaluation basic characteristics of a compact type semiconductor gamma camera (eZ-SCOPE AN) of Cadmium Zinc Telluride (CdZnTe). This new compact gamma camera has 256 semiconductors representing the same number of pixels. Each semiconductor is 2 mm square and is located in 16 lines and rows on the surface of the detector. The specific performance characteristics were evaluated in the study referring to NEMA standards; intrinsic energy resolution, intrinsic count rate performance, integral uniformity, system planar sensitivity, system spatial resolusion, and noise to the neighboring pixels. The intrinsic energy resolution measured 5.7% as FWHM. The intrinsic count rete performance ranging from 17 kcps to 1,285 kcps was evaluated, but the highest intrinsic count rate was not observed. Twenty percents count loss was recognized at 1,021 kcps. The integral uniformity was 1.3% with high sensitivity collimator. The system planar sensitivity was 33,330 cpm/MBq with high resolution collimator and 766,767 cpm/MBq with high sensitivity collimator. The system spatial resolution (FWHM) was 2.0 mm and 2.2 mm when the distance between source and collimator was 0 cm and 3 cm respectively.

Cadmium Compounds↗